Jethiga Sateeshkumar v Wigan Metropolitan Borough Council

X’s land is infested with Japanese Knotweed (“JKW”). Before X has knowledge of the infestation, the knotweed spreads to adjoining land which belongs to Y. Y sues X seeking both damages for the diminution in the value of Y’s land caused by the spread of JKW from X’s land and the cost of eradicating the knotweed from Y’s land. There is no evidence that either the diminution in value or the cost of eradicating the knotweed is any greater for any continuing breach of duty after X has the relevant knowledge necessary to give rise to liability in nuisance. Following the decision of the Supreme Court in Davies v Bridgend Council [2024] UKSC 15, the claim in respect of the diminution in value must fail. But what of the claim for the cost of eradication? That issue, which was alluded to but not determined by the Supreme Court in Davies v Bridgend, is the subject matter of this appeal.

The Claimant/Respondent lives at 18 Leighton Street, Atherton. She has owned the freehold since 2008. To the west of her land is an open area of grassland including a children's playground known as Vulcan Park. This land is owned and maintained by the Defendant/Appellant (Footnote: ¹). It is common ground that for some time the Defendant’s land was the site of JKW, which in due course spread onto the Claimant’s land.

An information paper on JKW published by the Royal Institution of Chartered Surveyors (“RICS”) in 2012 is summarised thus by Sir Terence Etherton MR in the case of Williamsv Network Rail Infrastructure Ltd [2018] EWCA Civ 1514, itself a case relating to JKW.

“[3] The RICS paper describes Japanese Knotweed as a hardy bamboo-like perennial plant which grows quickly and strongly and spreads through underground roots or rhizomes. Rhizomes are similar in their effects to roots, being underground stems which themselves produce fine, white, hair-like roots. Its thick clumps and stands can quickly grow to a height of over two metres… The roots can extend up to seven metres horizontally and three metres vertically… The most severe category of risk presented by knotweed is where the knotweed is within seven meters of a habitable space. The RICS paper states that knotweed can affect drains, patios, paths, drives, boundary walls, retaining walls, outbuildings, conservatories and drives. It can block drains; disrupt drain runs; grow between slabs of concrete drives; disrupt brick paving; undermine garden wall; and overwhelm poorly built outbuildings and conservatories… [5] …once it is established, ‘eradication requires steely determination’.”

By a Claim Form issued on 6 April 2024, the Claimant sought “damages and injunctive relief arising from a nuisance caused by Japanese Knotweed.” The Particulars of Claim plead the factual background to the case and the existence of a continuing nuisance by reason of the presence of the JKW on both the Claimant’s property and the Defendant’s land. The Claimant’s losses are particularised as being the cost of treating JKW on her land so as to eradicate it (£2,635) and the diminution in the value of her property as a result of the infestation, assuming that the defendant instructs a suitably qualified contractor to treat the JKW on the defendant’s land in accordance with a treatment plan. (For the avoidance of doubt, the term “infestation” is not defined in the Particulars of Claim, but the document refers to infestations both on the Claimant’s land – see [5.4] – and the Defendant’s land – see [5.1] and [5.2].)

In an admirably clear and well-reasoned judgment, the judge found the following key facts:

From these findings, the Judge concluded:

The Defendant appeals with permission of His Honour Judge Ranson on a single ground:

“The Judge erred in law in finding that there was a continuing nuisance or that the Claimant was entitled to recover the cost of treating Japanese knotweed on her land. To recover the cost of herbicide treatment as the cost of abating a continuing nuisance, the Claimant had to show some causative link between a breach of the duty by the Defendant and the presence of knotweed on her land. On the facts found by the Judge, causation was not made out.”

The Claimant contends that this in fact amounts to two grounds of appeal:

I heard the appeal on 5 May 2026. Both counsel had filed clear skeleton arguments and I was assisted by their succinct but insightful advocacy.

It is common ground that this is an appeal on a point of law where the appellate court must itself determine whether the grounds for the claim were properly made out. Accordingly, unlike in appeals that are concerned with findings of fact or the exercise of an evaluative judgment, there is limited scope for deference to the lower court.

In Williams, Sir Terence Etherton MR considered the nature of private nuisance and identified five principles of the cause of action as follows:

In Williams, the Court of Appeal concluded that, contrary to the finding of the Recorder at first instance, the presence of JKW on the defendant’s land (which neighboured the claimant’s land) was not an actionable nuisance on account of it reducing the value of the claimant’s land, on the ground that, as Sir Terence Etherton MR put it at [48], “the purpose of the tort of nuisance is not to protect the value of property as an investment or financial asset. Its purpose is to protect the owner of land (or a person entitled to exclusive possession) in their use and enjoyment of the land as such a facet of the right of ownership or right to exclusive possession. The decision of the recorder in the present case extends the tort of nuisance to a claim for pure economic loss.”

However, the tort of nuisance does extend to a landowner who, being aware of the presence of JKW on its land and of the risk of it encroaching on to neighbouring land, fails to take reasonable steps to prevent that encroachment and its consequent interference with the right of the neighbouring landowner to enjoy their land. As Sir Terence Etherton MR put it at [55]: “Japanese Knotweed was rightly described by the recorder at para 5, as ‘a pernicious weed’. It does not only carry the risk of future physical damage to buildings, structures and installations on the land. Its presence, and indeed the mere presence of its rhizomes, imposes an immediate burden on the owner of the land in terms of an increased difficulty in the ability to develop, and in the cost of developing, the land, should the owner wish to do so. Japanese Knotweed and its rhizomes can fairly be described in the sense of the decided cases, as a ‘natural hazard’. They affect the owner’s ability fully to use and enjoy the land. They are a classic example of an interference with the amenity value of the land.”

It follows from the decision in Williams that, in so far as a landowner proves the encroachment onto their land of JKW (or its rhizomes) from neighbouring land and at a time when the neighbouring landowner knew or ought to have known of its presence and ought to have taken steps to eradicate it, the owner of the land onto which the JKW has spread has a good claim against its neighbour in private nuisance. This principle is not in issue in the present case.

It is further not in dispute that, in so far as the Claimant here proves loss that arose after the Defendant became in breach of duty (through the combination of knowledge or the means of knowledge of the presence of JKW on the defendant’s land and a reasonable opportunity to eradicate the JKW before it spreads to the claimant’s land), the Claimant may recover such loss whether it be by way of damages for diminution in the value of the land caused by the encroachment or the cost of eradicating the JKW that is present because of such encroachment.

However, what is in issue is the liability of the defendant for the cost of eradicating JKW that encroached before the defendant’s breach of duty arose.

A starting point for considering the issue that arises here, namely what is the extent of that liability in terms of the cost of eradicating JKW from land on to which it has encroached, is to look at the decision of the Supreme Court in Davies v Bridgend [2024] UKSC 15. The claimant in that case owned land in Nant-y-moel. The defendant local council owned the adjourning land. At a date described in the judgment as “well before 2004”, JKW, which had previously been growing on the defendant’s land, encroached onto the claimant’s land. On thefindings of the judge (that were not interfered with on appeal), the defendant became liable to the claimant for the continuing nuisance in 2013 when it was or ought to have become aware of the risk of damage and loss of amenity to the claimant’s land by reason of the presence of JKW on its land, but failed to take steps to abate that nuisance by implementing a reasonable and effective treatment programme.

The claimant’s case at trial was that, because of the presence of JKW on the claimant’s land, the value of that land was adversely affected. The defendant did not dispute the finding that there was a continuing nuisance from 2013 to 2018 but argued that any diminution in value was caused by the presence of JKW on the claimant’s land (as it was put in the judgment, “well before 2004”) prior to the time of any actionable tort on the part of the defendant (which was 2013), and that any nuisance thereafter was irrelevant to the claimant’s loss.

The Claimant had also claimed treatment costs of £3,600, being the amount which on the evidence was necessary to treat JKW on the claimant’s land. At trial, it was conceded on his behalf that, if the JKW had spread to the claimant’s land before the defendant was in breach of duty through the failure to eradicate the plant, the claimant could not recover treatment costs. The concession is explained in the summary of the argument advanced by counsel for the claimant at page 438F-H of the report in the Appeal Cases.

“At trial, the claimant accepted that since Japanese Knotweed had encroached before the breach, he would have had to incur the cost of treatment. The cost of treatment was incurred but for any breach because treatment costs are binary: once incurred, that is it. The position in respect of a residual diminution in value is different. Where a property has had JKW, it is treated and there is then a remaining stigma. The starting point must be that the stigma will decrease over time. It was incumbent on the defendant to rebut that starting point with evidence that residual diminution in value would last forever, which it did not do. The defendant’s case, which rests on asserting that residual diminution in value was a binary loss, because once incurred it would always stay the same, is flawed.”

Whether this concession in fact reflects good law is the very issue that arises in this case.

In Davies, the District Judge at first instance dismissed the claim and the claimant’s appeal to the circuit bench was unsuccessful. However, the claimant succeeded on his appeal to the Court of Appeal, only to find that judgment overturned by the Supreme Court which reinstated the original judgment dismissing the claim.

The primary issue in the appeal in Davies was whether the residual diminution in value was caused by the defendant’s tort. It was argued by the claimant and accepted by the Court of Appeal, that the decision of the House of Lords in Delaware Mansions Ltd v Westminster City Council [2001] UKHL 55 is authority for the proposition that “a claimant is entitled to recover the reasonable costs incurred in abating a continuing nuisance” (see Lord Stephens at [66], with whose judgment the majority concurred). However, as Lord Stephens went on to say at [67], “a loss representing a diminution in market value is not an aspect of reasonable costs incurred in abating a continuing nuisance. Delaware is not authority for the proposition that diminution in market value is recoverable, regardless as to whether the diminution occurred prior to the Defendant’s breach of duty.”

On the findings of the judge of first instance in Davies, the Supreme Court held that “the application of the ‘but for’ test in this case eliminates the defendant’s subsequent breach of duty as a causative factor.” Hence the appeal was allowed and the claim for this head of loss failed.

It is clear that the Supreme Court’s decision on this issue in Davies resolved the like issue in this case as to the claim for diminution in value, namely whether a landowner can be liable for causing a diminution in the value of neighbouring land which occurred before the relevant breach of duty. It is unsurprising, on the findings of the District Judge in this case, that the claimant has not challenged the dismissal of the claim for diminution in value on appeal since Davies is binding authority against the claimant’s case on this issue.

The decision in Davies left open the issue that arises in this case. In his judgment in that case at [35], Lord Stephens described the concession referred to at [19] above as having the effect that, if the JKW had spread to the claimant’s land before the defendant was in breach of duty through the failure to eradicate the plant, the claimant could not recover treatment costs:

“No issue arises on this appeal as to whether the concession was correct or whether the claim for the costs of treatment might be recoverable as a reasonable cost incurred in abating the nuisance…”

Lord Burrows (who concurred with the conclusion of Lord Stephens but gave a separate judgment) said, when dealing with the proper application of the “but for” test of causation to the facts of the case:

“Applying the ‘but for’ test to the facts of this case, the breach of duty from 2013 did not factually cause the residual diminution in value of the land. The Claimant has not proved that the residual diminution in value would not have been suffered but for the breach of duty. This was because the JKW was already presenton the claimant’s land before 2013 so that the residual diminution in value had already been brought about by the natural, non-actionable, encroachment of the JKW. Indeed the claimant conceded at trial that he was not entitled to damages for the cost of treatment of the JKW because that cost was not factually caused by the breach of duty. The cost of treatment would have had to be incurred irrespective of the breach of duty. Yet, inconsistently, that concession was not extended to the residual diminution in value: in this case, the correct position as regards factual causation is that what applies to the cost of treatment applies equally to residual diminution in value.”

One might read this as an expression of opinion by Lord Burrows that the concession was properly made in respect of the claim for the cost of treatment on the basis that this cost was no more caused by the defendant’s breach of duty than the diminution in value of the claimant’s land, both being losses that the claimant would have suffered regardless of the defendant’s breach of duty because the causative encroachment had taken place before the defendant’s date of knowledge. But Mr Swirsky for the Claimant urged on me caution about making assumptions as to Lord Burrows’ reasoning when he had not expressly said that the concession was properly made, and in any event noted that the judgment of Lord Burrows on this issue was the obiter dicta of a single justice of the Supreme Court. I agree with him that I should look at the issue as a matter of principle, without speculating as to what Lord Burrows may have been thinking, however distinguished a lawyer he may be.

The Claimant contends that the continued presence of JKW on the defendant’s land amounts to a continuing nuisance; that the defendant has knowledge of its presence and the continuing nuisance that it has created; and that therefore the defendant is liable for the cost of treating the claimant’s land so as to eradicate the JKW on its land. The first of these propositions is self-evidently correct (though for reasons that I will explore, care is needed with the use of the phrase “continuing nuisance.”). The second proposition is conceded on the findings of Judge Powell. The third proposition is the point at which the parties part company.

The concept of a rooted plant or tree causing nuisance on another’s land is well recognised. In Delaware Mansions v Westminster cited above, the roots of a plane tree growing on the defendant’s land had spread on to the claimant’s land. The encroachment of the roots, which led to them taking in water, caused the land to become desiccated such that three blocks of flats on the land of the second claimant (Flecksun) required underpinning works to their foundations. The trial judge found that the original encroachment of the roots had taken place before the second claimant had acquired ownership of the land and flats; that damage had already occurred by the time that the second claimant acquired ownership; and that the second claimant had not proved that any of the remedial work had been necessitated by new damage to the foundations caused after the second claimant had acquired ownership. Accordingly, the claim was dismissed.

The House of Lords held that the continuing presence of the tree amounted to a continuing nuisance since it continued to draw water from the claimant’s land. The mere fact that some of the damage may have been caused prior to the second claimant’s ownership of the land did not negate that conclusion. As Lord Cooke put it at [33]: “there was a continuing nuisance during Flecksun's ownership until at least the completion of the underpinning and the piling in July 1992. It matters not that further cracking of the superstructure may not have occurred after March 1990. The encroachment of the roots was causing continuing damage to the land by dehydrating the soil and inhibiting rehydration. Damage consisting of impairment of the load-bearing qualities of residential land is, in my view, itself a nuisance.”

On this analysis, Delaware is a clear case of a continuing nuisance because the presence of the plane tree and its roots were continuing to affect the claimant’s land. But one must look with some care at the concept of the “continuing nuisance” as demonstrated by the judgment of the Supreme Court in Jalla v Shell International Trading and Shipping Co Ltd [2023] UKSC 16. The case was concerned with oil that leaked from a flowline connecting the seabed from where the oil was being extracted from the Bonga oil field off the Nigerian coastline to a waiting oil tanker. The leak occurred over about 6 hours and reached the shoreline (and therefore the claimants’ land) within weeks of the spillage. More than six years after the leak the claimants sought permission to amend the claim to substitute a new defendant. They alleged that the claim was not time barred because it related to a continuing cause of action. This argument failed at first instance when Stuart-Smith J, as he then was, found that the escape of oil was a one-off nuisance that did not give rise to liability for a continuing nuisance but rather a cause of action that accrued once the claimants’ land was affected by the oil.

Both the Court of Appeal and the Supreme Court upheld this judgment. Three passages from the judgment of Lord Burrows with whom the remainder of the court agreed explain the Supreme Court’s reasoning:

The Claimant here contends that this is a case akin to the facts of Delaware. The relevant state of affairs which gives rise to liability is the presence of JKW and its rhizomes that originally had grown on the Defendant’s land, just as the plane tree in Delaware had grown on the defendant’s land. The spread of the JKW onto the Claimant’s land, as the spread of the roots of the plane tree in Delaware continues as a nuisance for which the defendant is responsible.

The Claimant accepts that JKW differs from a plane tree in that the latter may have spreading roots but remains a single trunk growing (on the facts of Delaware) on the defendant’s land, whereas the nature of JKW as a rhizomatous plant means that fresh stands of JKW can grow on the Claimant’s own land. Both within his skeleton argument and during oral submissions, counsel for the Claimant described the JKW on the Claimant’s land as being “the Defendant’s,” underlying the contention that any damage caused by the JKW on the Claimant’s land continued to be the responsibility of the Defendant.

The Claimant draws comparison with the position in Martin v Cooper [2024] EWHC 3296 where the claimant alleged (amongst other things) that the defendant had built up soil and constructed a garage on his land, causing damage to the claimant’s adjoining garden wall,in respect of which the claimant was entitled to the costs of the construction of a retaining wall to prevent future instability of the garden wall. In respect of this aspect of the claim, the defendant raised a limitation defence, alleging that the damage had occurred more than six years prior to the issue of the claim.

Freedman J rejected that defence, finding that this was a “continuing nuisance” in the sense referred to by Lord Burrows in Jalla. At [62], he stated that “the relevant damage was the cost of building a retaining wall, which was required following the effect of the continuing pressure from the build-up of soil and the garage and was in order to avoid future loss by ending the medium-term or long-term instability of the property, that is to avoid future loss.” Just as that case involved a continuing state of affairs in respect of which the claimant was entitled to relief with the cause of action accruing “afresh on a continuing basis” (as Freedman J put it at [62]), so the presence of JKW that originated on the Defendant’s land in the instant case is a continuing state of affairs with a similar continuing liability on the Defendant to meet the cost of remedial action.

The Claimant contends that the alternative result of there being no liability would involve a tremendous injustice since the Defendant, who was responsible for the presence of the JKW on the Claimant’s land, would escape liability for paying for its removal, but the Claimant would be required to fund that work.

The Defendant rejects the Claimant’s argument that there is a continuing nuisance for which the defendant is liable. The claim could only succeed if the claimant could show a causative link between the need for remedial work and an actionable breach of duty by the defendant. But this was not a finding that the Judge at first instance made. The evidence points to the fact that the Claimant had already incurred the loss which he seeks to recover at the time that the Defendant first had the requisite knowledge accompanied by inaction that gives rise to a claim in nuisance. Thus, the Defendant is not guilty of a continuing nuisance of the kind that Lord Burrows contemplated in Jalla might give rise to a liability for remedial costs.

The facts of the current case are not directly comparable with those of either Delaware or Jalla. Like Delaware, the court is concerned with growing flora, which has its origins on one person’s land but is causing continuing consequences on another’s. But unlike Delaware, the presence of the flora on the Claimant’s land is itself a cause of the nuisance which is independent of what is occurring on the Defendant’s land. This is a consequence of the rhizomatous nature of JKW, making the plant essentially self-sufficient on the claimant’s land such that destruction of the JKW on the Defendant’s land was not sufficient to prevent a continuing problem on the Claimant’s land and is demonstrated by the fact that the JKW on the Defendant’s land has been treated but the Claimant seeks the cost of treating her own land which remains contaminated.

Like Jalla, the nuisance alleged here continues to have consequences for the Claimant’s land even though it does not continue outside of that land. But unlike Jalla, the presence of the putative nuisance on the Claimant’s land was caused by the state of the Defendant’s land at the time that the nuisance on the Claimant’s land commenced and, at least until the JKW on the Claimant’s land developed rhizomes, its continued existence and spread was dependent on the presence of JKW on the Defendant’s land.

The present circumstances involve a state of affairs which rises because of an infestation from the Defendant’s land which in principle is capable of amounting to a nuisance (see Williams) but which continues to flourish on the Claimant’s land independently of that original cause. Neither Delaware nor Jalla deal with this scenario.

In my judgement, three factors point in favour of the Defendant’s contention that, for the claim to succeed, the Claimant must show “but for “ causation in the sense that she must be able to point to evidence that it was the Defendant’s breach of duty (rather than any broader allegation of action or inaction on its part) that led to the loss.

First, the very nature of the tort of nuisance is that it is concerned with ongoing activity which causes harm to the claimant’s land. As Lord Burrows says in his judgment in Jalla at [26], a continuing nuisance that gives rise to liability is where “outside the claimant’s land and usually on the defendant’s land, there is repeated activity by the defendant or an ongoing state of affairs for which the defendant is responsible which causes continuing undue interference with the use and enjoyment of the claimant’s land.” The presence of JKW on the Defendant’s land from 2018 may be a state of affairs for which the defendant is responsible but it is not “the state of affairs which is causing undue interference with the use and enjoyment of the claimant’s land”. That interference is caused by the presence of JKW on the Claimant’s own land. Thus, the cause of the loss lies outside of the scope of activity for which a neighbouring landowner such as the Defendant can be liable.

The decision of Freedman J in Martin v Cooper is not a like situation to this. There was in that case a continuing state of affairs on the defendant’s land that was creating instability on the claimant’s land. That is the classic example of a continuing nuisance as contemplated by Lord Burrows in his judgment in Jalla at [26].But it is not analogous to the situation here where the continuing state of affairs that it is sought to abate is taking place on the Claimant’s own land.

Second, if the Claimant’s reasoning is to be preferred, it would have a striking consequence for the nature of liability for the tort of private nuisance. Whilst tort law is generally concerned, as its name would suggest, with a liability that is fault-based, the liability here would be independent of fault, with the landowner liable to compensate for damage to a neighbour’s land through an obligation to meet remedial costs that could not have been avoided by the landowner taking greater care since the damage which led to the need to incur remedial costs, namely the spread of JKW onto the Claimant’s land, was caused before the Defendant is to be blamed for not dealing with it.

Third, and closely associated with the first and second, the landowner’s liability would arise at a time where the only way that he could effectively abate the nuisance would be to go onto the Claimant’s land to eradicate the JKW that had already spread there; thus the focus would not be on the Defendant’s use of its own land but rather on the actions it was able to take on someone else’s land. The Defendant’s ability to minimise its liability would be dependent on matters outside of its control, specifically the ability to get access to the Claimant’s land to eradicate the JKW. Of course, if a Defendant, aware of the liability for which the Claimant here contends, namely to eradicate JKW that is present on the Claimant’s land because of a spread from the Defendant’s land, makes the Claimant aware of its willingness to pay for the cost of eradication, the failure of the Claimant to take up the offer might amount to a failure reasonably to mitigate the loss. But it is perfectly possible that the Defendant would not even know of the spread of the JKW to the neighbour’s land so that it did not know of its liability to eradicate. Even if it was aware of the infestation of the Claimant’s land, it might be unable to trace the owner of the neighbouring land and therefore unable to discharge its responsibility.

Fourth, if the Claimant’s argument is preferred, it is difficult to see that its liability would end with the cost of eradicating the JKW on the Claimant’s land. If there was further spread from the Claimant’s land to land that neighboured her land but did not neighbour the Defendant (so that the spread must have been via the Claimant’s land) it is difficult to see that the cost of remedying this spread would not also lie within the scope of the Defendant’s liability. Whilst liability to a wide class of neighbouring landowners is not an unusual feature of liability in nuisance, the width of that class underlines the potential consequences referred to in the previous paragraph, where spread might be taking place without knowledge on the Defendant’s part.

I am not deterred from this conclusion by the Claimant’s appeal to the injustice of the situation if the Defendant is not found liable for the remedial costs. It is sadly the case that landowners sometimes have to fund remedial work that they could not have avoided but for which no one else is liable. As I have noted above, the central concept of nuisance, as identified by Sir Terence Etherton MR in Williams is reasonableness as between neighbours. In this case, it is not reasonable to impose liability on the Defendant for the remedial costs to the Claimant’s land because, by the time that the Defendant could reasonably have taken steps to avoid the spread of JKW, those remedial costs had already arisen because of the previous encroachment of JKW onto the Claimant’s land.

For these reasons, I am persuaded that the true extent of the Defendant’s liability is for losses (including the reasonable cost of eradicating JKW) incurred as a result of the spread of the JKW onto the Claimant’s land that would have been avoided had the Defendant not been in reach of duty, in other words, had the Defendant taken reasonable steps to eradicate JKW on its land once it was aware (or ought to have been aware) of the presence of the JKW on its land. On the facts as found by the Judge below, no such losses arose after the Defendant became in breach of duty by reason of its failure to act as a reasonable neighbour by eradicating JKW of which it knew or ought to have known, the JKW having by then already spread to the Claimant’s land.

It follows that, notwithstanding the conspicuously careful judgment at first instance, I allow the appeal.